1. Field of the Invention
The present invention relates to a light deflection element that reflects and deflects light of a laser beam or the like, and to a display uses such a light deflection element.
2. Description of the Related Art
Light deflection elements are used in scanners of optical equipment such as electronic photocopiers, laser beam printers and barcode readers, in optical deflection apparatus such as optical disk (disc) tracking controllers, and in display apparatus in which a laser beam is scanned and an image is projected.
Typical elements used as light deflection elements include a rotating polygonal mirror and a galvano mirror, the galvano mirror featuring the ability to make a more compact mechanism than in the case of a rotating polygonal mirror, and using recent semiconductor microprocess technologies there have been reports of micromirrors using silicon substrates, leading to the expectation of even further improvements in compactness, light weight, and low cost.
An example of the above-noted galvano mirror type of light deflection element is disclosed in the Japanese patent application laid-open publication H8-211320. In this related art example, when a voltage is applied between one fixed electrode and a reflective mirror, the left side of the reflective mirror is attracted because of an electrostatic force, so that the reflective mirror rotates in the counterclockwise direction about a pair of beams as an axis, and when a voltage is applied between another fixed electrode and the reflective mirror, the right side of the reflective mirror is attracted by an electrostatic force, so that the reflective mirror rotates in the clockwise direction about the pair of beams as an axis. Therefore, by applying alternately applying a voltage to a pair of fixed electrodes using a driving apparatus, it is possible to cause the reflective mirror to swing to the left and right. Light that is shone onto this reflective mirror is reflected at an angle that changes in accordance with the swing of the reflective mirror, the light being thereby deflected.
In the example of the past, however, to achieve a large swing (deflection) angle with a reflective mirror, it is necessary to establish a large gap between the reflective mirror and the fixed electrodes. However, because the electrostatic force is inversely proportional to the square of this gap, to achieve the required drive force, an extremely large voltage is required, thereby making this approach substantially impractical.
Another example of related art is disclosed in the Japanese patent application laid-open publication H8-334723. In this related art example, a drive apparatus has a pair of left and right permanent magnets disposed on a base and a drive coil disposed around the periphery of a reflective mirror, a drive current alternating between positive and negative being passed through this drive coil. In this configuration, when a drive current alternating between positive and negative is passed through the drive coil, a Lorentzian force generated because of the outer magnetic field of the pair of permanent magnets and the current through the drive coil act to cause the reflective mirror to swing about a pair of beams as an axis.
In the above-noted related art example, however, while because there is no limitation to the deflection angle such as in the case of the previously described electrostatic drive, it is possible to achieve a large deflection angle, because of the drive coil disposed around the periphery of the reflective mirror, the size of the reflective mirror increases, making this approach unsuitable for high-speed deflection.
Additionally, in both the cited related art examples, because drive force is directly applied to the reflective mirror, it is necessary to configure the drive apparatus so that it does not interfere with the swinging of the reflective mirror, this representing a limitation to the degree of freedom in configuring the drive apparatus.